For many years, most heavy duty, built, detergent compositions have been based upon anionic surfactants and they have been observed to cause some harshness in the feel of washed fabrics. Accordingly, there have been developed textile softening compositions, and these have been based upon long chain cationic surfactants. As cationic and anionic surfactants are generally incompatible, these softening compositions have been intended for use in the final rinse of a washing process, that is after substantially all the anionic surfactant has been removed. Clearly there is a need for a single composition able both to clean the fabrics and to soften them.
Attempts to incorporate cationic softeners in anionic based detergent compositions, overcoming their ordinary incompatibility, have been described in the art. Another approach has been to use nonionic surfactants with cationic softeners in built detergent compositions as described in Brit. Pat. No. 1,079,388, DTAS No. 1,220,956 and U.S. Pat. No. 3,607,763. However, products containing a high ratio of nonionic detergent to cationic softener are said to soften inadequately, whereas those with a high ratio of cationic to nonionic are said to clean inadequately. A particular problem in the use of such products has been the discolouration, usually yellowing, of repeatedly washed fabrics.
This problem is believed to arise from three causes. The first is the ineffectiveness of most of the usual optical brighteners when applied in the presence of cationic surfactants, due to the failure of the brightener to deposit upon fabrics in such surroundings and/or from an actual quenching of the fluorescence of the brightener in the presence of cationic surfactant. The second main cause of yellowing is build-up of the brightener itself, which in some circumstances can act as a dyestuff at visible wavelengths. The third cause is apparently an interaction between the cationic or nonionic-cationic surfactants and colouring matter in the water used to make up the wash baths. The extent of this problem depends upon the state of the civic water supply, and can vary from place to place and from time to time. Iron content may be one relevant factor, but probably organic, e.g. peaty colouring matter, is more usually the principal cause. Although exact mechanism is not known, it seems that the presence of the cationic softener component tends to aggravate the deposition of this and other solid suspended matter upon the washed fabrics, and to inhibit the removal of certain normally bleachable stains. The deposition of suspended matter can be reduced and the removal of bleachable stains improved, according to the present invention, by the inclusion of small amounts of a class of organic phosphonates in the composition.
Anionic based detergent compositions containing ethylene diamine tetra methylene phosphonate as a stabiliser for persalts are disclosed in British Pat. No. 1,392,284. Compositions containing anionic, amphoteric or nonionic surfactant, preferably at least half being anionic; a fabric softener comprising a specified condensation product of fatty glyceride and a hydroxyalkyl polyamine and optionally a di-long chain alkyl quaternary ammonium salt; and a foam inhibitor; are described in British Pat. No. 1,314,381. These compositions may contain a sequestering agent such as ethylene diamine tetra acetate, hydroxy ethane-1,1-diphosphonate or nitrilotrimethylene phosphonate.